Apparatus for generating video signals representing a photographic image previously recorded in a frame on a photographic film-type medium

ABSTRACT

Apparatus for generating video signals representing photographic images previously recorded in a frame on a photographic film-type medium includes an image pickup device which produces video signals in response to a light image of the projected photographic image, a digitizer which digitizes the produced video signals, a memory which stores a video frame interval of the digitized video signals, an enhancer which enhances digitized video signals read from the memory, and a digital signal processor which controls the image pickup device, the memory and the enhancer.

This application is a division of application Ser. No. 07/731,079, filedJul. 16, 1991, now U.S. Pat. No. 5,249,056.

BACKGROUND OF THE INVENTION

This invention relates to apparatus for viewing photographic imagespreviously recorded on a film-type medium and, more particularly, tosuch apparatus which converts film frame images to video signals fordisplay on a video monitor, also known as a cine-video conversionsystem.

Film viewing mechanisms having general application such as filmprojection systems are well known to those of ordinary skill in the art,particularly in the field of cinematography or the like. These systemsinclude a film transport mechanism and a projection mechanism, andtypically project an illuminated image of one film frame at a time on aviewing screen or an empty wall. A constant image of one particular filmframe may be viewed (as in a slide projector), or, more commonly, thesesystems are used to view images in motion. In particular, motion of theviewed image may be perceived by the viewer as a result of therepetitive projection of successive film frames which were originallyrecorded on the film in rapid succession.

Film projection systems, however, suffer from several drawbacks andlimitations. One such drawback is the problem of limited brightness,familiar to anyone who has been to a movie theater. This problem isinherent in the process of projecting light over a significant distance.Another limitation of merely projecting the light image of the filmframe is the fact that since the image is never "captured" by thesystem, either electronically or otherwise, there is no possibility ofprocessing or modifying the image to improve its quality or itsusability.

Recently, cine-video systems which convert the images recorded on filmto video signals in real time have been introduced as an alternative tostandard film projectors. With this type of system, the film frameimages are electronically "captured", so as to be represented byelectronic signals. These signals may be processed, if desired, andultimately, they are displayed on a standard video monitor, therebyeliminating some of the drawbacks of projected images. The basics ofsuch a cine-video system include a film transport mechanism, by whichthe film is loaded into the system and by which each film frame image ispositioned for projection, a projection mechanism, by which the filmframe image thus positioned is projected onto a video camera lens by anilluminating light source, and a video camera, by which the projectedimage is captured and converted to an electronic video signal.

One application of film viewing systems in general, and cine-videosystems in particular, is in the medical field, and, more particularly,angiography, such as in a cardiac catheterization laboratory forproducing high resolution displays on a standard video monitor from 35mm angiographic film. In this application in particular, the lack ofnumerous quality and usability features, not heretofore present ineither film projectors or prior cine-video systems, limits the value ofthese prior systems. For example, one of the major limitations of priorsystems is the inability to provide for a continuously variable viewingspeed (i.e., the number of consecutive film frames scanned by the filmtransport mechanism per second). In particular, although many of thesesystems allow for the viewing of motion at a few different film speeds,they generally do not provide for continuously variable speed viewing,as may be desired by the user, without loss of resolution.

Another drawback of the prior systems is their inability toelectronically enhance the quality or usability of the video image. Forexample, and particularly in medical applications, it is often the casethat the visibility of detail in the dark areas of high contrastpictures is limited. Electronic image enhancement techniques in whichcertain differences in brightness can be accentuated so as to providemore visibility of detail are not provided by prior systems. Althoughprior cine-video systems capture the image electronically and aretherefore not inherently restricted from providing such capabilities asare mere film projectors, none have done so to date.

Yet another drawback of the prior systems is their high cost andinflexibility relative to the capabilities and features they provide.The manufacturing cost of mechanical designs and analog electricalcircuitry implementation is far higher than the cost of digitalelectronics performing comparable functions. Moreover, the use ofdigital, programmable processors and associated software not onlyfurther reduces the cost, but also provides vastly superior flexibility,in that system functions can be added, replaced or modified easily andinexpensively. None of the prior commercially available film viewingsystems, neither film projectors nor prior cine-video systems, areimplemented as digital systems controlled by programmable digitalprocessors.

A further drawback of prior systems is the lack of a direct digitalvideo signal output, and particularly real time digital output, usefulfor applications such as recording on a digital VCR (video cassetterecorder) or for data analysis. Whereas mere film projectors bythemselves clearly cannot provide any output other than the viewableimage itself, cine-video systems typically do provide video signaloutputs. However, the prior cine-video systems do not provide any suchoutput in a digital video format.

Yet another drawback of prior systems is the lack of a "Hi-line" videosignal output, which allows for the images to be viewed on a multi-scanmonitor for improved quality. A Hi-line video signal provides for twicethe standard number of scan lines, and thereby increases the imagebrightness as well as the apparent resolution, and further reduces thenoticeability of raster scan lines. Again, whereas mere film projectorscannot provide output signals at all, cine-video systems do; however,the prior commercially available cine-video systems have provided onlystandard video signal outputs.

A still further drawback of prior systems is their inability to includeuser-locatable "cursor" marks overlaid on the image being viewed.Particularly in medical applications, and particularly when an image isbeing viewed and discussed by more than one medical professional, it isoften useful to be able to precisely identify one or more points ofparticular interest on the image. Prior film viewing systems provide nomechanism for overlaying such identifying marks on the image, andtherefore manual, imprecise tools, such as a hand-held pointer, must beused.

Yet another drawback of prior systems is the lack of any ability toprovide measurement information regarding the distance between a pair ofpoints on the subject of the image being viewed. Particularly in medicalapplications such as angiography, portions of the images viewedrepresent vessels or other anatomical elements whose absolute size orsize relative to other elements is of critical importance. Prior filmviewing systems provide no mechanism for making such measurementsaccurately, and therefore a combination of guesswork and manual,imprecise tools (e.g., a ruler used to measure portions of the viewedimage itself) must be used.

Still another drawback of prior systems is the lack of an electronicallycontrolled zoom capability for increasing and decreasing themagnification of the image being viewed. Prior systems have providedonly imprecise, manual zoom capabilities, if at all.

These aforementioned drawbacks of prior film viewing systems, both filmprojectors and prior cine-video systems, reduce the effectiveness andflexibility with which one may view and make use of photographic imagesrecorded on film. Particularly in medical applications such asangiography, the elimination of these drawbacks can provide for a farmore powerful tool for film viewing and analysis for the professionaluser.

OBJECTS OF THE INVENTION

Therefore, it is an object of the present invention to provide animproved apparatus for viewing photographic images previously recordedon film, in particular, a cine-video system, which overcomes theaforementioned drawbacks and limitations associated with prior art filmviewing apparatus.

Another object of this invention is to provide improved apparatus whichpermits film to be viewed in motion at continuously variable speedswithout loss of resolution.

Another object of this invention is to provide cine-video apparatus inwhich the quality or usability of an image is enhanced by accentuatingcertain differences in brightness in order to provide improvedvisibility of detail.

A further object of this invention is to provide cine-video apparatus oflow cost and high flexibility relative to its capabilities, by the useof digital electronics in general, and digital, programmable processorsand associated software, in particular.

A still further object of this invention is to provide cine-videoapparatus which includes a digital video signal output for use inrecording on a digital VCR, for data analysis or for archiving purposes.

Still another object of this invention is to provide cine-videoapparatus which includes a Hi-line video signal output containing twicethe standard number of scan lines for improved viewing quality.

An additional object of this invention is to provide cine-videoapparatus having user-locatable cursor marks overlaid on the image beingviewed, in order to accurately locate and identify points of particularinterest.

Yet a further object of this invention is to provide cine-videoapparatus which includes the ability to provide measurement informationregarding the distance between a pair of points on the subject of theimage being viewed.

Still another object of this invention is to provide cine-videoapparatus which includes an electronically controlled zoom capabilityfor increasing or decreasing the magnification of the image beingviewed.

Various other objects, advantages and features of the present inventionwill become readily apparent from the ensuing detailed description, andthe novel features will be particularly pointed out in the appendedclaims.

SUMMARY OF THE INVENTION

In accordance with this invention, an apparatus for generating videosignals from a photographic image previously recorded on film (acine-video system) is provided, which includes a film transportmechanism for advancing or rewinding the film in order to position afilm frame at a film gate for projection, an image projector whichdetects when a film frame is positioned at the film gate and projects anilluminated image of that frame, a video pickup system which receivesthe image and generates a video signal which represents it, and anoutput circuit which produces a resultant output video signal. Thus, anew image is received and a new video frame is generated, when a newfilm frame is positioned in the film gate.

As one aspect of this invention, the image projector is inhibited fromprojecting an illuminated image when the video pickup system is notready to receive a new image. In this manner, the integrity of eachimage is assured, regardless of the speed with which the film transportmechanism is advancing or rewinding the film.

As another aspect of this invention, the image projector repetitivelyprojects an illuminated image of the same film frame when the filmtransport is holding the film frame fixed at the film gate but varioususer adjustments are being made to the resultant image. This aspectenables the viewer to see the effects of these adjustments, even thoughthe system is in a "still frame mode."

As yet another aspect of this invention, the video pickup systemincludes provisions for the enhancement of the resulting video signal.This enhancement capability includes user-selectable gamma adjustmentfunctions which accentuate the differences in brightness in the darkerregions of the image, while compressing the differences in the brighterregions. This allows for greater visibility of detail in high contrastimages.

Still another aspect of this invention provides a cine-video systemwhich includes an image pickup system which receives a projected imageand generates video signals which represent that image, a windowgenerating capability with which the user can define a range of videosignal values within which an enhancement of video signals is to beperformed, and an enhancement capability which performs thatenhancement. This user-selectable enhancement capability includes, forexample, the ability to accentuate the differences in brightness withinthe given range of video signal values by "stretching" this range ofvalues into the full range of brightness values. Thus, the visibility ofdetail in a portion of the image of particular interest can be improved.Also included is the ability to invert the polarity of the image,thereby creating a "negative" image, and the ability to perform a gammaadjustment within a selected window.

As yet another aspect of this invention, a cine-video system is providedwhich includes an image pickup system which receives a projected imageand generates video signals which represent that image, a digitizer toconvert these video signals to digital form, a memory for storing avideo frame of digitized signals, an enhancement capability whichenhances the digitized video signals if desired, and a digital signalprocessor which controls the image pickup system, memory and enhancementcapability. By providing for a programmable, digital system, costs arereduced and flexibility is increased. This digital system may furtherinclude an output circuit which produces a video output in digitalformat.

Still another aspect of this invention is to provide a digitalcine-video system which includes an optical zoom capability for zoomingin and out on the image. By changing the magnification of the image inthis manner, a particular area of detail may be examined more closely.The zoom capability is under the control of the digital signalprocessor.

Another aspect of this invention is to provide a digital cine-videosystem which includes an optical panning capability for panning theimage. By using this feature in combination with the optical zoomcapability, any portion of the image may be examined in detail. Thepanning capability is under the control of the digital signal processor.

As yet another aspect of this invention, a cine-video system is providedwhich includes an image pickup system which receives a projected imageand generates video signals which represent that image, a memory inwhich the individual scan lines from the separate field intervals of thevideo signals generated for each film frame are separately stored,read-out circuitry by which the scan lines are read from the memory attwice the standard line repetition rate, and combining circuitry forselectively combining these lines of video signals from successive fieldintervals of at least one video frame to produce a resultant frame ofvideo signals formed of twice the standard number of scan lines. Thus, a"Hi-line" video signal is provided for use with video monitors whichprovides a significant increase in apparent resolution and reduces thenoticeability of raster scan lines.

Another aspect of this invention is to provide a cine-video system whichincludes an image pickup system which receives a projected image andgenerates video signals which represent that image, a memory for storinga video frame, cursor generation circuitry for selectively generatingone or more cursors, and circuitry to combine the video signals for thevideo frame with cursor signals to generate video signals whichrepresent the image with one or more cursor overlays superimposed on theimage. In this manner, a user may place cursors on the image at pointsof particular interest, for identification or discussion.

As still another aspect of this invention, the cine-video systemincludes a measurement capability with which the distance between twolocations in the subject of the image can be determined by placing acursor on the point in the image which corresponds to each suchlocation. In one embodiment a calibration capability is provided forrelating physical distances between locations in the subject of theimage with distances in the image itself, thereby determining actualdistance between the locations identified by the cursors. As analternative, the measurement provides only relative distance informationby comparing the distance between two locations in the subject of theimage with the distance between another two such locations.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example, will bestbe understood in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a cine-video system in which the presentinvention finds ready application;

FIG. 2 is a block diagram of a cine-video system according to thepresent invention;

FIG. 3 provides a more detailed description of the image projector andimage pickup system;

FIG. 4 is a block diagram which provides a more detailed representationof the video enhancement circuit;

FIG. 5 graphically illustrates several examples of useful enhancementfunctions provided for by the preferred embodiment of the videoenhancement circuit;

FIG. 6 is a block diagram of a preferred embodiment of the presentinvention which is implemented as a digital video system under thecontrol of a digital signal processor;

FIG. 7 is a block diagram which illustrates the feature of the presentinvention wherein "zooming" and "panning" of the displayed image areprovided;

FIG. 8 is a block diagram which details the generation of the "Hi-line"composite video output circuit;

FIG. 9 schematically shows the generation of Hi-line video output imagesaccording to one embodiment;

FIG. 10 schematically shows the generation of Hi-line video outputimages according to a second embodiment;

FIG. 11 is a block diagram depicting the operation of the presentinvention whereby one or more cursors may be overlaid, or superimposed,on the video image, and of the calibration and measurement functionswhereby relative or actual physical distances between two such cursorsmay be determined; and

FIG. 12 provides flow charts representing the manner in which thecalibration and measurement functions are performed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, wherein like reference numerals are usedthroughout, and in particular to FIG. 1, there is illustrated anapparatus for generating video signals from film in which the presentinvention finds ready application. The purpose of this cine-video systemis to generate video signals representing photographic images previouslyrecorded on conventional photographic medium, such as on conventional 35mm photographic film. The illustrated cine-video system is particularlyuseful in angiography, such as in the environment of a cardiaccatheterization laboratory; and the photographic images typicallyrepresent X-ray images of, for example, the cardiac system. It will beappreciated that the information represented by such X-ray orphotographic images is not critical to the present invention.

The illustrated cine-video system is comprised of a console 106 whichhouses a film transport assembly 19, a keyboard 42, a track ball 48, anda video imaging subsystem, and a separate video monitor 108. The filmtransport assembly is adapted to move film 14 bidirectionally between asupply reel 19s and a take-up reel 19t through a film gate 22 whichdefines an imaging station at which is positioned an optical imageprojector and a video image pickup device, such as a CCD camera or thelike. The manner in which the film transport assembly operates forms nopart of the present invention per se; but is the subject of copendingapplication Serial No. (Attorney's Docket 390103-2437), and is describedmore fully therein. As each photographic film frame is transportedthrough the film gate, an optical image thereof is projected to theimage pickup camera which generates video signals corresponding thereto;and these video signals are processed, stored and enhanced, and thendisplayed on monitor 108.

The video monitor may comprise a conventional NTSC monitor, a multi-scanmonitor or a high resolution monitor operable to display a video imagecomprised of twice the conventional number of horizontal raster lineswhich constitute a standard video image. The video image displayed onthe monitor may appear as a moving image if film 14 moves between thesupply and take-up reels; or the image may be displayed as a still imageif film 14 is stationary (still frame mode). The manner in which videosignals are generated to produce a video image comprises the presentinvention, and is described in detail below.

FIG. 2 is a block diagram of an apparatus for generating video signalsand video images from a photographic image previously recorded on afilm-type medium in which the present invention finds ready application.The illustrated apparatus is comprised of a film transport mechanism 19on which are mounted a supply reel 19s containing film 14 to be viewedand a take-up reel 19t, a sprocket 34, an image projector 13, an imagepickup system 15, a frame memory 16, a video enhancement circuit 18, anda video output circuit 20.

Film transport mechanism 19, which is described in greater detail in theaforementioned copending application, is adapted to advance or rewindfilm 14 by the coordinated rotation of supply reel 19s, take-up reel 19tand sprocket 34. The film has recorded thereon a series of uniformlyspaced image frames. A supply reel motor functions to drive the rotationof the supply reel and a take-up reel motor functions to drive therotation of the take-up reel for forward or backward movement of thefilm. Sprocket 34, which is physically coupled to the usual sprocketholes of film 14 is driven by a sprocket motor.

Image projector 13 is optically coupled to film transport mechanism 19,and is adapted to project, for a transitory duration, an illuminatedimage of a film frame, one frame at a time. According to a preferredembodiment of the present invention, the image projector projects animage when film 14 has been advanced or rewound by an amount equal to anintegral number of film frames. Preferably, image projector 13 iscomprised of a film motion sensor which detects the motion of sprocket34, and thereby detects the motion of film 14. Analysis circuitryresponds to the measured motion of film 14 to determine that the nextfilm frame is in proper position to be projected and thereby triggers astrobe light, which generates a flash of light at the proper time. In analternative embodiment of the invention, the strobe light may bereplaced by a shuttering mechanism which provides for the illuminationof the film frame from a constant light source for a transitoryduration. The shuttering mechanism may be any of a number of varietiesknown to those of ordinary skill in the art, such as electronicshuttering, LCD (liquid crystal diode) shuttering, gated imageintensifying, or the like. In any event, according to the presentinvention it is preferable that the illuminated image of a single filmframe be projected for a transitory duration, regardless of the meansused to accomplish this.

Image pickup system 15 is optically coupled to image projector 13 and isadapted to receive the illuminated image of the film frame produced byimage projector 13 and to generate a video signal representing thatimage. The image pickup system is comprised of a video camera whichreceives and captures the light image to produce a video signal output.In the preferred embodiment, the video signal output is subjected to agamma adjustment function, and an analog-to-digital converter provides adigital data representation of the captured image. Preferably, the videocamera is a standard CCD (charge coupled device) video camera, butalternatively it may be any other conventional video camera familiar tothose of ordinary skill in the art.

Gamma adjustment, which according to the present invention may or maynot be present, is intended to improve the quality of the video image bystretching the black region of the gray level (brightness) scale, whilecompressing the white region. Circuits which perform various gammaadjustment functions are familiar to those of ordinary skill in the art,but, in the preferred embodiment of the present invention, not only issuch a circuit included, but the specific gamma adjustment function tobe performed on the video signal is user-selectable from a predeterminedplurality of adjustment functions.

Frame memory 16 is electrically coupled to image pickup system 15 and isadapted to store the video data supplied by the image pickup systemwhich represents the video image of a single film frame produced in aresponse to a triggered strobe light. In the preferred embodiment of thepresent invention, this memory is implemented with standard video fieldmemories, but standard RAM (random access memory) devices or otherdigital or analog storage devices familiar to those of ordinary skill inthe art may be used in other embodiments.

Video enhancement circuit 18 is electrically coupled to frame memory 16and is adapted to increase the usefulness of the video images to beviewed by modifying the images in various user-selectable ways so thatimportant features of the image can be viewed more clearly. In thepreferred embodiment of the present invention, the video enhancementcircuit is comprised of a set of look-up tables adapted to convert thevideo data as it is read out of frame memory 16 into enhanced data,wherein the look-up tables are implemented with standard RAM.Alternatively, this data conversion may be accomplished with look-uptables or other circuitry implemented by alternate circuit arrangementssuch as ROMs (read-only memories), PALs (programmable logic arrays), orother programmable or non-programmable circuits familiar to those ofordinary skill in the art. In addition, this data conversion may beperformed partially or entirely by software executed on either aconventional general purpose or special purpose processor. In any event,according to the present invention, data enhancement is an optional, butdesirable, feature for modifying the digital frame data representing theimage of a film frame.

Video output circuit 20 is electrically coupled to video enhancementcircuit 18 and is adapted to produce one or more video output signals ina respective format for display on various types of video monitors orfor other use, such as for recording by a digital VCR (video cassetterecorder). In the preferred embodiment of the present invention, astandard format RS-170 composite video signal at a standard 525/60 Hzline rate (i.e., 525 scan lines each 1/30th of a second), a "Hi-line"composite video signal at twice the standard line rate (1050 scan lineseach 1/30th of a second), and a standard "D-2" format digital videooutput signal are produced. Other embodiments may produce other standardor non-standard video output signals useful for video display, videorecording or video analysis.

Preferably, video output circuit 20 is comprised of a digital to analogconverter to convert the digital frame data back to analog form,together with circuitry to add composite synchronizing and blankingsignals to both the RS-170 video signal and the "Hi-line" video signal.Circuitry to provide for user control of the video image brightnesslevel may also be included. In addition, a frame doubling memory may beprovided to store digital image data for two successive film frames foruse in the creation of the "Hi-line" video signal as will be describedfurther below.

In operation of the illustrated apparatus, film transport mechanism 19positions film 14 so that image projector 13 projects, for a transitoryduration, a light image of a single film frame onto the lens of thecamera included in image pickup system 15. In particular, imageprojector 13 projects the light image of the given film frame for abrief period of time sufficient to enable the video camera of imagepickup system 15 to capture and temporarily store that image.

Image pickup system 15, after capturing a video image, converts thecaptured image into data which represents that image, and which, in thepreferred embodiment of the present invention, is in digital form. Thisdigital data is supplied to frame memory 16, which stores and holds thedata until data representing another video image is supplied by imagepickup system 15.

Next, video enhancement circuit 18 enhances the video image if thesystem user so requests (as will be described), by modifying the datastored in frame memory 16 in order to provide resultant video images inwhich various features of the film frame to be displayed can be viewedmore clearly. In the preferred embodiment of the present invention, thedata is modified as it is read out of frame memory 16, butalternatively, the modified data stored in the frame memory may beeither modified in-place therein, or stored in a different memory aftermodification to be subsequently read out. Examples of enhancements whichvideo enhancement circuit 18 performs include conversion of the data torepresent a negative, rather than a positive, image. In addition, thoseportions of the video image which have gray levels of brightness outsideof a user-selectable range may be suppressed, while those portionshaving gray levels within the range may be mapped onto different levelsin such a manner as to enhance the distinctiveness between the levelswithin the range (i.e., the gray levels may be stretched). After thevideo data is processed by video enhancement circuit 18, video outputcircuit 20 converts the enhanced data to one or more video outputsignals for display on various types of video monitors or for recording,as by a digital VCR.

It will be appreciated that the system described herein is capable notonly of producing a viewable video image of a single film frame in stillmotion, but may also be used to produce viewable video images of asuccession of film frames driven in forward or reverse motion and atvarying film speeds. In particular, film transport mechanism 19 may beoperated to advance or rewind film 14 at a user-selectable speed, andimage projector 13 may, as a result, repeatedly cause images ofsuccessive film frames to be projected to image pickup system 15 one ata time, as each film frame passes the proper location or imaging stationfor projection, for example, a film gate. In this manner, frame memory16 operates to store a succession of different film frames. Meanwhile,however, the contents of frame memory 16 may be read out in anasynchronous manner with respect to the successive storing of theseframes. In particular, frames of video data are read out of frame memory16 at the standard video viewing rate of 30 frames per second, therebyallowing them to be displayed in succession on a standard video monitorby video output circuit 20, even though 30 film frames per second arenot necessarily imaged onto image pickup system 15.

It will be further appreciated that the series of multiple film framesprojected by image projector 13 and thereby ultimately displayed on avideo monitor may or may not be immediately successive frames asrecorded on film 14. Since at most 30 frames per second are processed byimage pickup system 15 in the preferred embodiment, and data from framememory 16 is read out at 30 frames per second, image projector 13 isinhibited in the preferred embodiment from projecting images at a fasterrate. Therefore, the image projection of some film frames will beskipped when film 14 is being advanced or rewound at a speed greaterthan 30 frames per second. When film 14 is advanced or rewound at aspeed less than 30 frames per second, on the other hand, frame memory 16may be read out multiple times for the same stored film frame image.Thus, when film transport mechanism 19 advances or rewinds film 14 atany given speed, the user may view a progression of frames, that is, amotion picture, moving in the corresponding direction and at thecorresponding speed as the film.

FIG. 3 provides a more detailed description of image projector 13 andimage pickup system 15 according to the preferred embodiment of thepresent invention. In particular, the illustrated image projector iscomprised of a film gate 22, a film motion sensor 24, a pulse generator26, a counter 28, a strobe generator 30, and a strobe light 32. Theillustrated image pickup system is comprised of a camera 36, anamplifier 38, and a gamma adjustment circuit 40, which is responsive toactivation of a keyboard 42.

Film gate 22 is physically coupled to film 14, and is adapted to providea pathway by which an illuminated image of a film frame, accuratelypositioned in the film gate, may be projected onto the lens of camera36.

Film motion sensor 24 is coupled to sprocket 34 and is adapted to senseand measure the rotation of sprocket 34, and thereby determine thedirection and amount by which film 14 has moved relative to film gate22. According to a preferred embodiment of the present invention, thefilm motion sensor is comprised of an electronic encoder which generatesquadrature pulse signals wherein the relative phase of the pulses (i.e.,which one of paired quadrature pulses precedes the other) indicates thedirection of rotation of sprocket 34, and the frequency of these pulsesindicates the speed of rotation of the sprocket. Alternatively, thedirectional and speed information may be encoded in any other mannerfamiliar to those of ordinary skill in the art.

Pulse generator 26 is electrically coupled to film motion sensor 24 andis adapted to convert the signals supplied by the film motion sensorinto counter control pulses which are used to determine the preciserelative location of a film frame of film 14 within film gate 22. In thepreferred embodiment of the present invention, the pulse generatorconverts the quadrature pulse signals supplied by film motion sensor 24into an individual up-count signal and a down-count signal for use by anup/down counter, and is implemented with a programmable logic device (inparticular, a PAL). Alternatively, other logic circuitry familiar tothose of ordinary skill in the art may be used.

Counter 28 is electrically coupled to pulse generator 26 and is adaptedto count pulses supplied by the pulse generator in order to determinewhen a film frame of film 14 is precisely located at film gate 22. Inthe preferred embodiment of the present invention, the counter isimplemented by a standard up/down counter, such as a Texas Instruments74LS193, but, alternatively, the counter may be implemented by otherlogic circuitry familiar to those of ordinary skill in the art, or thecounting function may be performed partially or entirely by softwareexecuted on either a conventional general purpose or special purposeprocessor.

Strobe generator 30 is electrically coupled to counter 28 and camera 36,and is adapted to generate a strobe pulse of a precise, transitoryduration in order to illuminate a strobe light so that a light image ofa film frame is projected onto the camera lens for that transitoryduration. The strobe generator may be implemented by any fixed-widthpulse generator familiar to those of ordinary skill in the art, such asa "one-shot" circuit (monostable multivibrator).

In a preferred embodiment of the present invention, strobe generator 30includes an inhibit input which, when activated, provides for thesuppression of the generation of a strobe pulse when camera 36 is notready to receive a new image. Where camera 36 is a conventional CCDvideo camera providing NTSC standard video signals, as it is in thepreferred embodiment, such a state of unreadiness may occur, forexample, during a brief portion of the vertical blanking period of theNTSC standard when the camera is in the process of loading its internalmemory from its CCD pickup elements. At that time, the camera is unableto capture an image, and therefore the strobe is inhibited. As anotherexample, the strobe is inhibited during a portion of the periodfollowing the point in time when the previous image has been captured(i.e., since the last strobe), while the camera is reading out thepreviously captured video data. Otherwise, if the camera capturesanother image, it would likely corrupt the integrity of the data beingread out. The implementation of this inhibit signal for both purposeswill be obvious to those of ordinary skill in the art, and may begenerated, directly or indirectly, by camera 36.

Furthermore, according to a preferred embodiment of the presentinvention, pulse generator 30 also includes a 30X strobe override signalinput. This signal, activated when film 14 is stationary relative tofilm gate 22 (still frame mode) and when user adjustments require thatthe video image nonetheless be updated, causes the strobe generator toemit strobe pulses repetitively at the rate of thirty times a second. Inthis manner, new video image data is stored in frame memory 16, and theeffects of user adjustments then being made (for example, gammaadjustments, focusing and image panning and zooming as discussed below)can be thereby instantaneously viewed by the user, despite the fact thatthe film frame being viewed has not itself been changed.

The fixed, predetermined width of the pulse generated by strobegenerator 30 (which establishes the period of time during which theilluminated image of a given film frame is projected) is sufficientlyshort to minimize any blurring of the image captured by camera 36, whichotherwise would occur at the higher speeds of motion of film 14 thatfilm transport mechanism 19 provides. Nonetheless, the strobe pulsewidth is sufficiently long so that the total quantity of light projectedonto the camera lens, when considered together with the illuminatingcharacteristics of the strobe light and the light sensitivitycharacteristics of the camera, is adequate. This determination may bemade using conventional analysis techniques familiar to one of ordinaryskill in the art.

Strobe light 32 is electrically coupled to strobe generator 30, and isadapted to illuminate, for the transitory duration established by thestrobe generator, the single film frame of film 14 which is located atfilm gate 22, and thereby briefly project an image of that film frameonto camera 36. As mentioned previously, in alternative embodiments ofthe invention the strobe light is replaced by a shuttering mechanismadapted to illuminate the film frame from a constant light source for asimilar transitory duration.

Camera 36 is optically coupled to strobe light 32 and film 14, and isadapted to receive and capture an illuminated image of the film framepositioned in film gate 22 and to generate a video signal whichrepresents that image. In the preferred embodiment of the presentinvention, camera 36 is a standard CCD video camera which produces anNTSC standard video output signal, such as a Sony XC-77 CCD black andwhite video camera. Alternatively the camera may be any otherconventional video camera familiar to those of ordinary skill in theart.

Amplifier 38 is electrically coupled to camera 36 and is adapted toamplify the video output signal produced by the video camera. Theamplifier may be implemented by a standard operational amplifier, suchas a VA2708 or equivalent.

Gamma adjustment circuit 40 is electrically coupled to amplifier 38 andis responsive to keyboard 42, and is adapted to provide the user withthe ability to improve the quality of the video image captured by camera36. In particular, gamma adjustment improves the visibility of detail inthe dark areas of high-contrast images, by stretching the black regionof the gray level (brightness) scale while correspondingly narrowing thewhite region. In a preferred embodiment, several gamma adjustmentfunctions are preselected, and the user of the system is able to selectwhich of these functions, if any, is to be applied to the video signalemitted by camera 36. The gamma adjustment functions are implementedwith standard analog components in a manner familiar to one of ordinaryskill in the art, and are selectable via an analog multiplexer, such asa 74HC4052, which the user controls via keyboard 42. As discussed above,when the user of the preferred embodiment changes the selection of gammaadjustment functions while the motion of film 19 is stopped (still framemode), it is desirable to at least momentarily activate the 30X strobeoverride input signal to strobe generator 30 to update the video imagestored in frame memory 16.

A description of the operation of the image projector 13 and the imagepickup system 15 as illustrated in FIG. 3 follows. As film transportmechanism 19 advances or rewinds film 14 as directed by the system user,film motion sensor 24, as a result of being coupled to sense therotation of sprocket 34, supplies quadrature pulse signals comprisingsprocket motion information to pulse generator 26. As a result, thedirection of film motion and the amount by which film 14 has moved aredetermined.

In response to the signals provided by film motion sensor 24, pulsegenerator 26 emits count pulses on the signal line which supplies theup-count signal to counter 28 while sprocket 34 rotates in the forwarddirection (e.g., counterclockwise). In one embodiment, 250 pulses aregenerated when film 14 advances by an amount equal to the film framepitch. Correspondingly, pulse generator 26 emits pulses on the signalline which supplies the down-count signal to counter 28 while sprocket34 rotates in the reverse direction (e.g., clockwise).

In order to simplify its implementation, in one embodiment of thepresent invention the circumference of sprocket 34 is of such a sizethat it makes n rotations to advance film 14 by one film frame. In thismanner, sprocket 34 may be provided with two independent sets of indiciaspaced equally around its circumference, where the corresponding indiciaof the respective sets are slightly displaced from one another. Thus,film motion sensor 24 need only detect the passing of these indicia assprocket 34 rotates to generate the quadrature pulses.

When counter 28 has counted, either as a result of up-count signalpulses, down-count signal pulses, or a combination of both (i.e., thedifference), the appropriate number of pulses from pulse generator 26(e.g., when it reaches the count of either positive or negative 250), itgenerates a signal which triggers strobe generator 30 to generate astrobe pulse which, in turn, energizes strobe light 32 to be illuminatedfor the appropriate transitory duration. Simultaneously, counter 28 isreset so that it may begin counting afresh in order to determine whenthe next film frame is precisely positioned for strobing. Thus, strobelight 32 flashes for successive film frames precisely when each frame ispositioned at film gate 22. It is appreciated that an initial adjustmentshould be made to accurately position one film frame at the imagingstation and thereby establish reference. This initial adjustment, knownas framing, may be performed by the user upon the initial loading offilm 14 into film transport mechanism 19, and again at any subsequenttime, if desired. In particular, the count value of counter 28 may beused as an offset by which the framing reference is established, byimplementing the counter as a cyclical counter of the appropriate numberof pulses (e.g., 250), and by using the count value at the time offraming as the value at which strobe pulses are triggered.

In the operation of image pickup system 15, camera 36 picks up the imageof the film frame positioned in film gate 22 and projected onto thecamera lens when strobe light 32 is triggered as aforesaid. The camerathen supplies output video data, in standard NTSC format, throughamplifier 38 and gamma adjustment circuit 40. The user of the system mayselect one of several predetermined gamma adjustment functions, or nogamma adjustment at all, by the use of keyboard 42. While camera 36 isin the process of reading out the video image data, it supplies aninhibit signal to strobe generator 30, thereby inhibiting strobe pulsesfrom being supplied to strobe light 32. This prevents the corruption ofthe video data in camera 36 when the motion speed of film 14 exceeds theframe rate at which the camera outputs video data (i.e., thirty framesper second).

FIG. 4 is a block diagram which provides a more detailed representationof video enhancement circuit 18 according to the preferred embodiment ofthe present invention. The illustration shows a track ball 48, a windowgenerator 46, keyboard 42, frame memory 16, a look-up table generator18a and a look-up table 18b.

Track ball 48 is a conventional user input device adapted to provide aconvenient means for entering continuous two-dimensional numerical data.It is comprised of an approximately hand-sized round ball, raisedslightly above a mounting platform, and supported to be easily rotatedin an arbitrary direction by the user's hand. The track ball is astandard commercially available computer input peripheral device, whichperforms functions similar to those of the computer "mouse" and"joystick", and may be easily interfaced for application by one ofordinary skill in the art. Although the preferred embodiment of thepresent invention uses track ball 48 as the user-input medium, it willbe apparent that an alternative medium, such as a "mouse", a "joystick"or a keyboard, may be used if desired.

Window generator 46 is responsive to track ball 48 and is adapted toproduce a minimum gray level and a maximum gray level, thus defining a"window" of gray levels upon which a selectable video enhancementfunction is to be performed. In the preferred embodiment of the presentinvention, vertical movement about the "x--x" axis of track ball 48adjusts the size of the window (i.e., the difference between the minimumgray level and the maximum gray level to open and close the window),whereas horizontal movement about the "y--y" axis of the track balladjusts the center value of the window (i.e., the location of the windowon the gray scale). Preferably, the function of window generator 46 isimplemented by a suitable program executed on a general purposeprocessor (an 8031 CPU). However, it will be appreciated that the windowgenerator may be implemented by other means, such as circuitry whichconverts the user-input data to the window data.

Look-up table generator 18a is illustrated as being functionally coupledto window generator 46 and keyboard 42, and is adapted to determinevideo signal data conversion functions which improve the usefulness ofthe video images to be viewed by modifying the images in varioususer-selectable ways so that important features of the image can beviewed more clearly. In the preferred embodiment of the presentinvention, the look-up table generator is readily implemented bysoftware executed on a general purpose processor (an 8031 CPU). Based onthe "window" supplied by window generator 46 and the specificenhancement technique selected by the user via keyboard 42, the look-uptable generator determines the specific gray level conversion(enhancement) function to be performed.

After the conversion function is selected, look-up table generator 18aloads data representing that conversion into look-up table 18b, to bedescribed below. With this approach, the look-up table may be loadedwith a desired enhancement function, i.e., a function converting eachpossible video signal value (gray level) in the video data to someresultant video signal value. The discussion of FIG. 5 below sets outexamples of those enhancement functions provided for in the preferredembodiment. The look-up table data to be loaded can be quite small,since the number of possible video signal values is usually limited. Forexample, in the preferred embodiment of the present invention there areonly 256 possible digitized values, each representing one of 256possible gray levels. Alternative embodiments may implement look-uptable generator 18a by means other than software, such as circuitrywhich generates the conversion data and loads it into look-up table 18b.Such implementations will be apparent to those of ordinary skill in theart.

Look-up table 18b is coupled to look-up table generator 18a and framememory 16, and is adapted to convert the video data read from the framememory into enhanced data based on the conversion function datapreviously loaded by look-up table generator 18a. In the preferredembodiment, look-up table 18b is implemented as two independentmemories. At any given time, only one of these memories is used toconvert video data into enhanced data. Meanwhile the other memory isavailable to be loaded with new conversion data by look-up tablegenerator 18a. In this manner, until the look-up table generatorcompletes the loading of the other memory, the video data being read outfrom frame memory 16 is not corrupted by being converted by partiallyincomplete conversion function data. Look-up table 18b may beimplemented with standard RAM devices (two CXK5814P memories), as in thepreferred embodiment of the present invention, but may alternatively beimplemented by other programmable or non-programmable circuitrycomprised of other devices such as ROMs, PLAs, or other standardcomponents familiar to those of ordinary skill in the art. Furthermore,there need not be any physical look-up table or equivalent hardwarecircuitry at all, as the entire data conversion process may be performedpartially or entirely by software executed on either a conventionalgeneral purpose or special purpose processor. Such alternativeembodiments will also be apparent to those of ordinary skill in the art.In addition, although the preferred embodiment modifies the video dataas it is read from frame memory 16, other embodiments may convert thevideo data to enhanced data by modifying the data stored in the framememory in-place, by modifying the data as it is written into anothermemory, or by still further alternative arrangements.

In operation of the apparatus illustrated in FIG. 4, the user selectsone of several predetermined video enhancement modes via keyboard 42,for example, a window mode, and then uses track ball 48 to set the upperand lower limits of the window via window generator 46. Look-up tablegenerator 18a then determines the conversion function (i.e., theresultant output video signal value for each possible input video signalvalue) and loads conversion data into look-up table 18b. When video datais subsequently read from frame memory 16, look-up table 18b convertsthat video data to video output data which has been enhanced by theenhancement mode selected by the user.

FIGS. 5A-5F graphically illustrate several examples of useful videoenhancement functions provided for by the preferred embodiment of thepresent invention. One particularly useful form of video enhancement isto "stretch" a user-selected window of gray levels into the full rangeof black to white, while blanking (changing to black) all gray levelsoutside of that window. FIGS. 5A, 5B and 5C are graphical depictionswhich show the resultant effect of this enhancement technique on theinput gray levels with three differently chosen windows. In thesegraphical representations, the input video data read from the framememory is plotted on the "x" axis, while the resultant enhanced videooutput data is plotted on the "y" axis. In each case the gray levelsbelow the window minimum and above the window maximum, if any, areblanked out, while the gray levels within the window are stretched fromblack at the window minimum to white at the window maximum. In thismanner, when viewing a film frame in which those areas of interest arewithin a given window of gray levels (brightness), the distinctionsbetween the various gray levels within that window can be exaggerated,and portions of the image which are brighter or darker than those ofinterest are eliminated from the displayed video image.

As shown in FIG. 5D, the black to white gray levels can be reversed bythe use of a different enhancement function, thus creating a negativeimage for viewing. In addition, as shown in FIG. 5E, this polarityinversion enhancement technique can be combined with the aforementionedwindow stretching technique in such a manner as to create a "stretched"negative image within a given gray level window. It will be noted thatin this case, since the enhanced image is polarity-inverted, theportions of the original image which are brighter or darker than thosewithin the window are converted to white, not black levels.

In the preferred embodiment of the present invention, gamma adjustmenttypically is performed by gamma adjustment circuit 40 within imagepickup system 15. Alternatively, gamma adjustment may be provided as avideo enhancement function, as shown in FIG. 5F. In particular, by usingthe window generation capability of window generator 46, a "stretched"gamma function enhancement may be performed on only that portion of theimage which is of interest, i.e., only within a specified gray levelwindow. Gray levels outside of the selected window are blanked. Otherenhancement functions may be provided with embodiments of the presentinvention.

FIG. 6 is a block diagram of a preferred embodiment which is implementedas a digital video system under the control of a digital signalprocessor 52. The apparatus includes an analog to digital converter 50,frame memory 16, video enhancement circuit 18, video output circuit 20,and digital signal processor 52.

Analog to digital converter 50 is coupled to image pickup system 15 andis adapted to convert the analog video signals generated by the imagepickup system to digital signals. In the preferred embodiment of thepresent invention, the image pickup system generates pixel data and eachpixel is converted to an 8-bit digital signal, thereby providing for therepresentation of 256 different gray levels (i.e., levels ofbrightness). The analog to digital converter is implemented by astandard device (such as a CXA1096P), but may be replaced by otherembodiments of analog to digital conversion circuitry familiar to one ofordinary skill in the art.

Frame memory 16 is coupled to analog to digital converter 50 and todigital signal processor 52, and is adapted to store the digitizedpixels which represent the video image of a single film frame.

Video enhancement circuit 18 is coupled to frame memory 16 and todigital signal processor 52, and is adapted to enhance the digitizedpixels based on the specific enhancement function selected, as describedabove.

Digital signal processor 52 is coupled to image projector 13, imagepickup system 15, digital frame memory 16 and video enhancement circuit18, and is adapted to control the operation of the digital video system.As is known, a digital signal processor (DSP) is a special purposeprogrammable processor designed for applications involving themanipulation of digital signals. The DSP used to implement digitalsignal processor 52 in the preferred embodiment of the present inventionis a Texas Instruments 320C25, but may alternatively be any otherdigital signal processor heretofore or hereinafter devised and familiarto those of ordinary skill in the art. In other embodiments, anyconventional general purpose or special purpose programmable processoror combination of processors may be substituted for digital signalprocessor 52.

As was described above, video output circuit 20 is coupled to videoenhancement circuit 18, and is adapted to produce one or more videooutput signals including, in particular, a digital video output signalin "D-2" standard format which may be used for recording by a digitalVCR such as the Sony DVR-10 or may be used directly by other digitalvideo products adhering to the D-2 standard.

In operation, the output of image pick-up system 15 is converted todigital video signals by analog to digital converter 50, and theresultant digital signal data for a given film frame is stored in framememory 16. When subsequently read from the frame memory, this digitalvideo data is processed by video enhancement circuit 18 which producesenhanced digital video data in the manner discussed above. Video outputcircuit 20 then formats this enhanced data to produce one or more videooutput signals, and may also reconvert the digital video data back to ananalog video format, thereby providing one or more analog video outputsignals as well.

In the preferred embodiment of the present invention, the operation ofthe digital video system shown in FIG. 6 is controlled by digital signalprocessor 52 which may control some or all of the various functionsperformed by the system and described herein. For example, the selectionof the gamma adjustment function to be applied by gamma adjustmentcircuit 40 of image pickup system 15 may be controlled by the processorin response to the user's requests via keyboard 42. The loading andreading out of the digital video data in frame memory 16 is controlledby the processor 52. The operation of video enhancement circuit 18 mayalso be controlled by the processor in response to the user's requestsvia keyboard 42 and the windowing data supplied by window generator 46in response to the user's input via track ball 48. In particular, theprocessor may be used to implement look-up table generator 18a asdescribed above, and/or the process of loading look-up table 18b withthe conversion data as also described above may be controlled byprocessor 52. The processor may also control both the inhibit signalinput and the 30X strobe override signal input to strobe generator 30 ofimage projector 13. It is recalled that the inhibit signal is producedin response to "camera-not-ready" data which may be supplied by camera36 of image pickup system 15, and the 30X strobe override signal isproduced when, for example, the user effects adjustments during a stillframe mode. In addition, processor 52 may control various otherfunctions performed by the system in a manner which will be readilyapparent to one of ordinary skill in the art. For example, the processormay control the setting of the focus adjustment of camera 36, as well asthe setting of the camera iris (i.e., the diameter of the lens openingwhich thereby determines the quantity of light which enters the lens),each in response to user requests, entered, for example, via keyboard42.

FIG. 7 is a block diagram which illustrates the feature of the presentinvention wherein "zooming" and "panning" of the displayed image areprovided. That is, a portion of the film frame which is displayed to theuser on a video monitor may be magnified by the use of an image zoommechanism, and that portion of the magnified image which is displayedmay also be moved up, down, left or right (i.e., image pan). This imagezoom and pan subsystem is comprised of digital signal processor 52, alens motor 55, camera 36 containing a camera zoom lens 36l, a cameratable motor 53, a camera table 54, a sprocket motor 56, and sprocket 34.

Digital signal processor 52 is coupled to keyboard 42, track ball 48,lens motor 55, camera table motor 53 and sprocket motor 56, and in thecontext of the image zoom and pan subsystem is adapted to control theoperation of the lens motor, camera table motor and sprocket motor inresponse to user requests supplied through the keyboard and track ball.

Lens motor 55 is coupled to digital signal processor 52 and is adaptedto control the magnification setting of camera zoom lens 36l in responseto the input signals it receives. In the preferred embodiment of thepresent invention, the lens motor is integral to the Sony XC-77 videocamera used to implement camera 36, but alternatively, either adifferent video camera with an integral zoom lens motor may be used, orlens motor 55 may be an independent servomotor familiar to those ofordinary skill in the art, which is mechanically coupled to camera zoomlens 36l.

Camera 36 which is optically coupled to film 14 and image projector 13,is physically coupled to camera table 54. The camera includes camerazoom lens 36l which is coupled to lens motor 55 and is adapted toincrease and decrease, within defined limits, the magnification of thefilm frame image projected onto the lens by the image projector. Thus,as the magnification of the image is increased, a smaller portion of thefilm frame positioned at film gate 22 is captured by the camera andthereby becomes the video image, and as the magnification is decreased,a larger portion of the film frame is captured as the video image.

Camera table motor 53 is coupled to digital signal processor 52 and isadapted to control the movement and thereby the "x--x" position ofcamera table 54 relative to film 14 in response to the input signals itreceives. In the preferred embodiment, the camera table motor iscomprised of a Yaskawa Electric FB5-20E type DC servomotor, but mayalternatively be implemented with any other comparable servomotorfamiliar to those of ordinary skill in the art.

Camera table 54 is mechanically coupled to camera table motor 53 andsupports camera 36. The camera table is adapted to shift or repositionthe camera mounted thereon which, because of the arrangement of the filmframes recorded "sideways" on the film, pans the video image along the"x--x" axis (i e., "X-pan") . More specifically, as camera 36 is shiftedin a direction perpendicular to the axis of motion of film 14, thatportion of the film frame positioned at film gate 22 whose illuminatedimage is captured by the camera is correspondingly shifted, therebyresulting in motion to the left or to the right in the video image.

Sprocket motor 56 is coupled to digital signal processor 52 and isadapted to control the rotation of sprocket 34 and thereby the motionand position of film 14. In the context of the image zoom and pansubsystem, the sprocket motor is particularly adapted to produce smallrotation adjustments of the sprocket, specifically within limitscorresponding to the length of a single film frame as recorded on film14. In this manner, the film is subjected to small adjustments along the"y--y" axis of the video image and the precise relative location betweeneach frame of film 14 and film gate 22 is shifted by a correspondingamount in the corresponding direction. In the preferred embodiment ofthe present invention, the sprocket motor is implemented with a YaskawaElectric FB5-20E type DC servomotor, but may alternatively beimplemented by other servomotors familiar to those of ordinary skill inthe art.

Sprocket 34 is mechanically coupled to sprocket motor 56 and physicallycoupled to the sprocket holes of film 14, and is adapted to control themotion and position of film 14. Fine adjustments of the rotationalposition of sprocket 34 by sprocket motor 56 pan the video image alongthe "y--y" axis (i.e., "Y-pan"). More specifically, as sprocket 34 isrotated slightly in either direction, film 14 advances or rewindsslightly, and, therefore, that portion of the film frame positioned atfilm gate 22 whose illuminated image is captured by camera 36 is shiftedin a corresponding direction and by a corresponding amount. Since thefilm frames are recorded "sideways" on the film, this slight movementresults in upward or downward motion in the video image. In thepreferred embodiment of the present invention, a given setting of thefilm panning position may be stored for future retrieval. In particular,the X-pan position is stored by recording the position of camera table54, while the Y-pan position is stored by recording the value of counter28 of image projector 13 (which represents the position of sprocket 34),thereby providing an alternative framing reference as described in thediscussion of FIG. 3 above.

In operation of the image zoom and pan subsystem in the preferredembodiment of the present invention, the user presses either the zoomkey or the pan key on keyboard 42. In response, digital signal processor52 causes the system to enter the zoom mode or the pan moderespectively, in either case activating track ball 48 for further userinput. In the zoom mode, the user then adjusts the track ball either bymoving it up to increase the magnification provided by zoom lens 36l, ordown to decrease the magnification. Digital signal processor 52 respondsto the track ball input to drive lens motor 55 to adjust the zoom lensaccordingly. In the pan mode, the user adjusts track ball 48 in any ofits possible directions (vertically, horizontally, or a combination ofvertical and horizontal movement). In response, digital signal processor52 first separates the horizontal component of the track ball motionfrom the vertical component. It then drives camera table motor 53 toadjust the position of camera table 54, and thereby the position ofcamera 36 relative to film 14, in accordance with the horizontalcomponent of the track ball motion (X-pan). The processor also drivessprocket motor 56 to adjust the rotational position of sprocket 34, andthereby the relative position of each film frame of film 14 with respectto film gate 22, in accordance with the vertical component of the trackball motion (Y-pan).

In this manner, within the limitations of the magnification power (i.e.,the maximum zoom capability) of camera zoom lens 36l, the user mayselect that portion of the film frame that he or she wishes to view, andmagnify it so that it fills the viewing screen. It is to be appreciatedthat, since the resolution of the image on film 14 typically is higherthan the resolution of camera 36 or the video monitor on which the imageis viewed, the resolution of that portion of the image or images whichhave been optically magnified will be proportionally increased, therebyallowing the user to see additional detail in the magnified image.

As discussed above, when the user of the preferred embodiment of thepresent invention is modifying the zoom and pan settings while themotion of film 14 is stopped (still frame mode), it is advantageous toactivate the 30X strobe override input signal to strobe generator 30 ofimage projector 13. As a result, the system updates the video imagestored in frame memory 16 with each strobe pulse, and thus, the user isable to view immediately the effects of the zoom and/or pan settingadjustments being made. It is to be appreciated that even though zoomand pan adjustments preferably are made while the motion of film 14 isstopped (still frame mode), film motion may be resumed while maintainingthe same user-selected zoom and pan settings. In the preferredembodiment specific zoom and pan settings may be stored and thereafterrestored after further modifications to these settings, simply bypressing a reset key on keyboard 42.

FIG. 8 is a block diagram which details the generation of the "Hi-line"composite video output signal by video output circuit 20. Theillustration shows frame memory 16 as being comprised of a field 1memory 16a and a field 2 memory 16b; and a portion of video outputcircuit 20 as being comprised of frame doubling memory 44 and doubledvideo generator 58. Frame doubling memory 44 is, in turn, comprised of afield 1 frame X memory 44a, a field 2 frame X memory 44b, a field 1frame Y memory 44c, and a field 2 frame Y memory 44d.

Frame memory 16 is adapted to store a single frame of video datasupplied by image pickup system 15 in two separate "interleaved" fields,field 1 and field 2, as is conventional. Preferably, field 1 memory 16ais specifically adapted to store the first field of the video datasupplied by image pickup system 15, and field 2 memory 16b isspecifically adapted to store the second field of the supplied videodata. In the preferred embodiment, field 1 memory 16a and field 2 memory16b are each implemented with standard video field memories (forexample, two CXK1206M devices each), but other storage devices familiarto those of ordinary skill in the art may alternatively be used.

Frame doubling memory 44 is coupled to video enhancement circuit 18 andis adapted to store video image data for each of the two fields of twosuccessive film frames. The data stored in the frame doubling memory isread out at twice the rate that the data is written therein. Framedoubling memory 44 is comprised of field 1 frame X memory 44a, which isadapted to store the first field of the video data for one of the twoaforementioned successive film frames, field 2 frame X memory 44b, whichis adapted to store the second field of the video data for the same oneof the two successive film frames, field 1 frame Y memory 44c, which isadapted to store the first field of the video data for the other of thetwo aforementioned successive film frames, and field 2 frame Y memory44d, which is adapted to store the second field of the video data forthat other film frame.

It will be appreciated that in the preferred embodiment of the presentinvention, neither the frame X doubling memories (field 1 frame X memory44a and field 2 frame X memory 44b) nor the frame Y doubling memories(field 1 frame Y memory 44c and field 2 frame Y memory 44d) alwayscontain the earlier of the two successive film frames, but, rather,their roles in this regard alternate. In particular, in order to providefor increased efficiency of operation, if the video data of the first oftwo successive film frames is stored in frame X memories 44a and 44b,and the video data of the second film frame is stored in frame Ymemories 44c and 44d, for example, then when a new (third) film frame isimaged and captured, it is stored in frame X memories 44a and 44b, sothat the frame Y memories now contain the earlier of the two successivefilm frames. It will also be seen that the aforementioned film framesare successive to the extent that the video image data which representsthem are successively stored in frame memory 16; but they need notnecessarily be successive film frame images as recorded on film 14. Inparticular, there may be numerous other film frame images recordedbetween them on the film (as might occur during high speed film motion),or, they may in fact be the same film frame as recorded on the film (aswould be the case in still frame mode).

In order to provide the video data for the Hi-line video output signalat twice the standard line rate, frame doubling memory 44 is implementedwith memory devices capable of reading out the data stored therein attwice the rate that the data is written therein. Thus, it is preferablethat these devices include independent clock inputs for reading andwriting data. In the preferred embodiment of the present invention, theframe doubling memories are implemented by standard video field memories(a total of eight 4C1050 devices), but other storage devices which maybe independently written to and read from, which are familiar to thoseof ordinary skill in the art, may alternatively be used.

Doubled video generator 58 is coupled to frame doubling memory 44, andis adapted to generate a Hi-line video output signal at twice thestandard line rate (1050 scan lines each 1/30th of a second) byselectively combining the video signal data included in separate videofields stored in the frame doubling memory, thereby improving thequality of the generated video image. In a first embodiment of thepresent invention, doubled video generator 58 produces, for each filmframe, a video image of the frame comprising all 525 lines, which isoutput twice in succession for (non-interleaved) display on a multi-scanmonitor. As a result of the fact that the entire image is displayedtwice in the same amount of time normally used to display a video imageonce (1/30th of a second), the resultant image is brighter, thenoticeability of raster scan lines is reduced, and there is asignificant increase in the apparent resolution. It is to beappreciated, however, that as a result of frame doubling memory 44 andthe doubled output speed, the Hi-line video output signal generated isdelayed by one frame (i.e., 1/30th of a second) as compared to thestandard video output signal.

In a second embodiment, doubled video generator 58 produces, for eachfilm frame, two output fields in sequence, which, when interleavedaccording to the NTSC standard and displayed on a high resolutionmonitor, constitute an entire image comprised of 1050 lines. Each ofthese output fields is formed of twice the number of lines (525)contained in each input field of the individual film frames (which isformed of 262.5 lines). In this second embodiment, the first outputfield which is generated by doubled video generator 58 is comprised ofalternating lines selected from the two input fields of a given filmframe. That is, if frame X memories 44a and 44b contain the video datafor the given film frame, the first of the two output fields generatedby doubled video generator 58 is comprised of alternating lines of videodata selected from field 1 frame X memory 44a and field 2 frame X memory44b, respectively, thus producing an output field of 525 lines.Correspondingly, if frame Y memories 44c and 44d contain the video datafor the given film frame, the first of the two output fields iscomprised of alternating lines of video data selected from field 1 frameY memory 44c and field 2 frame Y memory 44d, respectively.

In this second embodiment of the present invention, the second of thetwo output fields generated by doubled video generator 58 is produced bymixing certain lines from the subsequent film frame with certain linesfrom the given film frame. More specifically, field 1 of the subsequentfilm frame is alternated with field 2 of the given film frame. That is,if frame X memories 44a and 44b contain the video data for the givenfilm frame, and frame Y memories 44c and 44d contain the video data forthe subsequent film frame, the second of the two output fields generatedby doubled video generator 58 is comprised of lines of video dataselected from field 1 frame Y memory 44c alternating with lines of videodata selected from field 2 frame X memory 44b, respectively.Correspondingly, if frame Y memories 44c and 44d contain the video datafor the given film frame, and frame X memories 44a and 44b contain thevideo data for the subsequent film frame, the second of the two outputfields generated by doubled video generator 58 is comprised of lines ofvideo data selected from field 1 frame X memory 44a alternating withlines of video data selected from field 2 frame Y memory 44d,respectively.

In this manner, doubled video generator 58 in the second embodimentproduces a Hi-line output video signal which not only provides for avideo image comprising twice the standard number of lines, but improvesthe overall quality of video images which are in motion by allowingvideo signals derived from one frame to slightly permeate the display ofthe video signals derived from the previous frame. In particular, oneout of four of the lines of each film frame viewed will in fact beselected from the corresponding portion of the next film frame to beviewed.

In yet another (third) embodiment, the second output field is producedby combining the lines of both fields (i.e., fields 1 and 2) of thesubsequent film frame, rather than using the lines of field 1 of thesubsequent film frame with the lines of field 2 of the given film frame.This alternative equally mixes the video data from the subsequent filmframe with the video data from the previous one, but has thedisadvantage that yet an additional delay of one frame must be incurred,and, moreover, additional frame doubling memory is required, in order toensure that all of the field 2 video data of the subsequent frame hasbeen stored in frame doubling memory 44 before doubled video generator58 reads that data out.

Doubled video generator 58 is implemented in the preferred embodiment asa portion of a Xilinx XC3020 programmable ASIC (application specificintegrated circuit), but may alternatively be implemented by othercircuitry and/or software executed on a conventional general purpose orspecial purpose processor, familiar to those of ordinary skill in theart.

The operation of the Hi-line generator illustrated in FIG. 8 accordingto the aforementioned first embodiment is best appreciated by referenceto FIG. 9, which schematically shows the generation of a Hi-line videooutput image according to this embodiment. As the video image data for agiven film frame of film 14 is read out of camera 36 of image pickupsystem 15 and stored in frame memory 16, the horizontal scan lines ofvideo data which make up the image are separated into two fields, eachrepresenting alternating lines of the video image, as defined by theNTSC standard. Thus, when the video data representing film frame A,containing horizontal scan lines A1, A2, A3, A4, A5, A6, . . . , isstored in frame memory 16, the data for lines A1, A3, A5, . . . isstored in field 1 memory 16a, and the data for lines A2, A4, A6, . . .is stored in field 2 memory 16b. When the video data for film frame A issubsequently read out from frame memory 16, each of the two fields ofdata is stored separately in frame doubling memory 44, either in frame Xmemory 44a and 44b, or in frame Y memory 44 c and 44d, depending onwhere the data last read out was stored. In particular, if the videodata from the immediately preceding frame read out from frame memory 16had been stored in the frame X doubling memory, then the data from field1 memory 16a is written in field 1 frame Y memory 44c, and the data fromfield 2 memory 16b is written in field 2 frame Y memory 44d. If, on theother hand, as is assumed in the illustration, the video data from theimmediately preceding frame read out from frame memory 16 had beenstored in the frame Y doubling memory, then the data from field 1 memory16a is written in field 1 frame X memory 44a, and the data from field 2memory 16b is written in field 2 frame X memory 44b.

Next, as the video data for the subsequent film frame is being read outfrom frame memory 16 and stored in frame doubling memory 44, doubledvideo generator 58 generates doubled video frame 64 by alternatelyreading out the contents of field 1 frame X memory 44a and field 2 frameX memory 44b, where the data for the given film frame, frame A, wasstored. As a result, doubled video frame 64 is comprised of horizontallines A1, A2, A3, A4, A5, A6, . . . , twice the normal number of linesin a field, and the same as the total number of lines in a completeframe. Since frame doubling memory 44 is read out at twice the rate thatdata is stored therein, only field 1 of the video data for thesubsequent film frame has been stored (in field 1 frame Y memory 44c)when doubled video generator 58 has completed the generation of doubledvideo frame 64. Therefore, while field 2 of the video data for thesubsequent film frame is being stored in field 2 frame Y memory 44d,doubled video generator 58 generates doubled video frame 64 again. Inthis manner, lines A1, A2, A3, A4, A5, A6, . . . , which comprise allthe lines of the video image of film frame A, are displayed twice insuccession by the (non-interlaced) multi-scan monitor, both of whichoccur within the time normally used to display all the lines of an imageonce (1/30th of a second).

It will be seen that doubled video frame 64 need not be stored in amemory. That is, doubled video generator 58 produces the Hi-line videooutput signal directly by reading the video data out of frame doublingmemory 44 in the sequence described, and, in order to produce aresultant analog video signal, supplies the digital video data through adigital to analog converter, to which composite synchronizing andblanking signals are added.

An alternative operation of the Hi-line generator illustrated in FIG. 8,according to the second embodiment, is best appreciated by reference toFIG. 10, which schematically shows the generation of two successiveHi-line video output images, based on three successive film frames, A, Band C of film 14. Although, as pointed out above, the successive filmframes used to create the Hi-line images need not be successive asrecorded on film 14, they are illustrated as such for the sake ofsimplicity. It will be recognized that the bold horizontal lines in theillustration serve to separate portions of the diagram which representthe same physical or conceptual entity at different points in time.

As the video image data for each film frame of film 14 is read out ofcamera 36 of image pickup system 15 and stored in frame memory 16, thehorizontal scan lines of video data which make up the image areseparated into two fields, each representing alternating lines of thevideo image, as defined by the NTSC standard, and as described above.Thus, when the video data representing film frame A, containinghorizontal scan lines A1, A2, A3, A4, A5, A6, . . . , is stored in framememory 16, the data for lines A1, A3, A5, . . . is stored in field 1memory 16a, and the data for lines A2, A4, A6, . . . is stored in field2 memory 16b. When the video data for film frame A is subsequently readout from frame memory 16, each of the two fields of data is storedseparately in frame doubling memory 44, either in frame X memory 44a and44b, or in frame Y memory 44c and 44d, depending on where the data lastread out was stored. In particular, if the video data from theimmediately preceding frame read out from frame memory 16 had beenstored in the frame X doubling memory, then the data from field 1 memory16a is written in field 1 frame Y memory 44c, and the data from field 2memory 16b is written in field 2 frame Y memory 44d. If, on the otherhand, as is assumed in the illustration, the video data from theimmediately preceding frame read out from frame memory 16 had beenstored in the frame Y doubling memory, then the data from field 1 memory16a is written in field 1 frame X memory 44a, and the data from field 2memory 16b is written in field 2 frame X memory 44b.

Next, when the video data representing film frame B, containinghorizontal scan lines B1, B2, B3, B4, B5, B6, . . . , is stored in framememory 16, the data for lines B1, B3, B5, . . . is stored in field 1memory 16a, and the data for lines B2, B4, B6, . . . is stored in field2 memory 16b. When the video data for film frame B is subsequently readout from frame memory 16, each of the two fields is again storedseparately in frame doubling memory 44, in this case in frame Y memory44c and 44d, since the video data for film frame A was last stored inthe frame X doubling memory. That is, the data from field 1 memory 16ais written in field 1 frame Y memory 44c, and the data from field 2memory 16b is written in field 2 frame Y memory 44d.

As the video data for film frame B is being stored in frame doublingmemory 44, doubled video generator 58 generates Hi-line video outputimage 68 (i.e., the first of the two illustrated in FIG. 10). Inparticular, the doubled video generator first generates doubled videofield 1 66a by alternately reading out the contents of field 1 frame Xmemory 44a and field 2 frame X memory 44b, thereby creating the firstoutput field 66a which ultimately constitutes half of interlaced Hi-linevideo output image 68. It is recognized that since the video data forthe current film frame, frame B, is being stored in frame Y memories 44cand 44d, the doubled video generator generates its first output field66a from frame X memories 44a and 44b, where the data for the previousfilm frame, frame A, was stored. As a result, doubled video field 1 66ais comprised of horizontal lines A1, A2, A3, A4, A5, A6, . . . , twicethe normal number of lines in a field, and the same as the total numberof lines in a normal complete frame.

Since frame doubling memory 44 is read out at twice the rate that datais stored therein, only field 1 of the video data for film frame B hasbeen stored (in field 1 frame Y memory 44c) when doubled video generator58 has completed the generation of doubled video field 1 66a. Therefore,while field 2 of the video data for film frame B is being stored infield 2 frame Y memory 44d, doubled video generator 58 generates thesecond field 66b of the two doubled video fields. To avoid timingproblems, field 2 of the video data for film frame B is not used in thegeneration of this Hi-line video output image in the aforementionedsecond embodiment. Thus, doubled video generator 58 generates doubledvideo field 2 66b by alternately reading out the contents of field 1frame Y memory 44c, which contains the video data for field 1 of filmframe B, and field 2 frame X memory 44b, which still contains the videodata for field 2 of film frame A. As a result, doubled video field 2 66bis comprised of horizontal lines B1, A2, B3, A4, B5, A6, . . . , alsotwice the normal number of lines in a field. Therefore, when the twodoubled video fields 66a and 66b are combined, they contain twice thetotal number of lines in a normal complete frame.

Since doubled video field 1 66a and doubled video field 2 66b aregenerated by doubled video generator 58 in succession, the resultingdisplay on a high resolution interlaced monitor, according to the NTSCstandard, is the video image which results from interleaving thehorizontal lines of these two doubled fields. That is, Hi-line videooutput image 68 appears on the monitor as comprised of the horizontallines A1, B1, A2, A2, A3, B3, A4, A4, A5, B5, A6, A6, . . . , thuscreating an effective double-line image of film frame A with every otherline of film frame B permeating into every fourth line, and therebyimproving the overall quality of the video images when in motion.

It will be seen that neither doubled video fields 66 nor Hi-line videooutput image 68 need be stored in a memory. That is, in theaforementioned second embodiment, doubled video generator 58 producesthe Hi-line video output signal directly by reading the video data outof frame doubling memory 44 in the sequence described, and, in order toproduce a resultant analog video signal, supplies the digital video datathrough a digital to analog converter, to which composite synchronizingand blanking signals are added.

The lower half of FIG. 10 shows the generation of a second Hi-line videooutput image 68, which is based on the video data derived from filmframe B and film frame C. Since the process is identical to thatdescribed in detail above, however, it need not be repeated. The purposeof this portion of the illustration is merely to show the switching ofthe roles of the frame X doubling memories and the frame Y doublingmemories, which occurs in the generation of alternate Hi-line videooutput images. Although the preceding discussion describes in detail theimplementation of the line-doubled video signal generation technique ofthe present invention according to two specific embodiments, numerousother approaches to the generation of such video signals will be obviousto those of ordinary skill in the art.

FIG. 11 is a block diagram depicting the operation of the presentinvention whereby one or more cursors may be overlaid, or superimposed,on the video image, and relative or actual physical distances betweentwo such cursors may be determined. The preferred embodiment as depictedprovides for two independent cursors, and as a result, is comprised of acursor generator 62 which includes a cursor 1 locator 62a, a cursor 2locator 62b, and a cursor image generator 62c, a cursor overlay circuit60, a calibration and measurement processor 70, a zoom position sensor37, and an alphanumeric display 74.

Cursor 1 locator 62a is responsive to keyboard 42 and track ball 48, andis adapted to select a first cursor to be overlaid on the display of thevideo image of the film frame being viewed and to locate that cursor ata user-selectable location on the video image. In the preferredembodiment, the user activates cursor 1 positioning mode by pressing acorresponding cursor 1 key on keyboard 42, whereupon cursor 1 locator62a is enabled to accept signals from track ball 48 in order todetermine the location on the video image whereat cursor 1 ispositioned. In particular, the location of cursor 1 is continuallyrepositioned by cursor 1 locator 62a (and thereby continually displayedon the video image as a result of cursor image generator 62c and cursoroverlay circuit 60, as described below) and, therefore, the cursor movesabout on the video image as the user continues to operate track ball 48.When the user ceases to move the track ball, cursor 1 is "locked" inplace at its current location, and the cursor 1 positioning mode isdeactivated. In the preferred embodiment, cursor 1 locator 62a isimplemented with software executed on the Texas Instruments 320C25digital signal processor, but alternatively may be implemented withsoftware executed on other special purpose or conventional generalpurpose processors, or by discrete circuitry known to those of ordinaryskill in the art.

Cursor 2 locator 62b is responsive to keyboard 42 and track ball 48, andis adapted to select a second cursor to be overlaid on the display ofthe video image of the film frame being viewed and to locate that cursorat a user-selectable location on the video image. The operation andimplementation of cursor 2 locator 62b and the cursor 2 positioning modeis identical to that of cursor 1 locator 62a and cursor 1 positioningmode, and, therefore, it is unnecessary to describe the operation indetail again.

Cursor image generator 62c is coupled to cursor 1 locator 62a and cursor2 locator 62b, and is adapted to generate cursor image location datawhich represents the pixel locations of the video image which are to beoverlaid by the display of the cursor image or images. The output ofcursor image generator 62c in the preferred embodiment is comprised of xand y pixel location data which represents the actual video imagelocation of each activated cursor formed by a small grid of pixels (7vertically by 5 horizontally) where that cursor is to be located. Inparticular, this location data enables cursor overlay circuit 60 toreplace those few pixels of the video image data for the film framebeing viewed which are located at these pixel locations (i.e., those atwhich the image of cursor 1 or cursor 2 is to be overlaid), by the imageof the cursor or cursors themselves.

In the preferred embodiment of the present invention, cursor imagegenerator 62c is implemented by circuitry comprised of standardcomponents (such as 8254 counter/timer devices, 74LS191 counters, and aprogrammable PAL). By synchronizing its timing to the simultaneouslyoccurring process of reading the video image data from frame memory 16to video output circuit 20, this cursor image location generationcircuitry determines when the video data for each pixel location atwhich one of the cursor images is to be overlaid (based on the locationinformation supplied by cursor 1 locator 62a and cursor 2 locator 62b)is being transferred through cursor overlay circuit 60, and, when it is,that video data is replaced by video data representing a point of brightintensity (white). In this manner, the resultant video image isidentical to the video image of the film frame being viewed except forthe few pixels which contain the bright white image of the cursor orcursors (whose image is a cross-hatch pattern in the preferredembodiment). However, cursor image generator 62c may alternatively beimplemented by different means, such as software executed on aconventional general purpose or special purpose processor and/ordifferent circuitry known to one of ordinary skill in the art, whichprovides cursor image location information to cursor overlay circuit 60.

Cursor overlay circuit 60 is coupled to video enhancement circuit 18 andcursor image generator 62c, and is adapted to replace those pixels ofthe video image data which are located at positions at which the imageof each of cursor 1 and cursor 2 are to be located with video datarepresenting a point of bright intensity. The cursor overlay circuitreceives an input signal from the cursor image generator indicatingwhether to merely pass the video data for the current pixel of the imageof the film frame being viewed, or to replace the video data for thatpixel with the video data representing the white cursor. In this manner,the resultant video image is identical to the video image of the filmframe being viewed, except for the fact that the cursor or cursors havebeen overlaid onto the image.

Zoom position sensor 37 is coupled to camera zoom lens 36l of camera 36,and is adapted to determine the zoom setting of the lens. In particular,the zoom position sensor supplies as output the magnification factorprovided by the zoom lens. In the preferred embodiment, zoom positionsensor 37 is comprised of a conventional potentiometer, but mayalternatively be implemented by other circuitry familiar to those ofordinary skill in the art.

Calibration and measurement processor 70 is coupled to cursor 1 locator62a, cursor 2 locator 62b, keyboard 42, track ball 48 and zoom positionsensor 37, and is adapted to determine relative or absolute physicaldistances between a pair of points on the video image on which the userhas located cursor 1 and cursor 2 respectively. In particular, afterhaving located the cursors at each of two respective points a knowndistance apart (e.g., across the known diameter of the image of acatheter in a cardiac catheterization laboratory application), the usermay calibrate the system by using keyboard 42 to select a calibrationmode, and then by adjusting track ball 48 to perform the calibration.More specifically, when the user selects calibration mode, an initial(arbitrary) distance is displayed on alphanumeric display 74. Then, asthe user adjusts track ball 48, the distance displayed is modified inresponse to the track ball motion. When the distance displayed onalphanumeric display 74 agrees with the actual known physical distancebetween the two points located by the cursors, the user may "lock-in"the calibration via keyboard 42. Once this calibration has beenperformed, the system is enabled to accurately determine the distancebetween any other two points that the user wishes to measure. It will beappreciated that the physical distance between pixels in the verticaldirection does not equal the physical distance between pixels in thehorizontal direction, but, nonetheless, the relationship between thesedistances is fixed and known.

Calibration and measurement processor 70 is also responsive to the zoomsetting of camera zoom lens 36l in the preferred embodiment. Inparticular, when the calibration operation is performed by the user, thethen existing zoom setting (i.e., the magnification factor) is suppliedto the calibration and measurement processor by zoom position sensor 37.The zoom setting is thus taken into account in determining therelationship between the distance between pixels in the image and theabsolute physical distance between points in the subject of the image,by multiplying the distance between pixels determined without regard tothe zoom setting times the magnification factor. In this manner, theresultant calibrated distance between pixels represents the distancebetween pixels for a x1 zoom setting (i.e., no magnification of theimage). When the setting of camera zoom lens 36l is subsequentlymodified by the user and a measurement of the physical distance betweentwo cursor locations is performed, calibration and measurement processor70 readjusts the relationship between pixel distance and physicaldistance accordingly. In particular, the calibrated distance betweenpixels (as determined above) is multiplied by the pixel distance betweenthe two cursor locations, and the result is divided by the magnificationfactor supplied by zoom position sensor 37 at the time of themeasurement. Therefore, it is not necessary for the calibrationoperation to be performed again as a result of changes in the zoomsetting.

After the calibration operation has been performed, the user may makemeasurements by moving the cursors to desired locations, and thenselecting a measurement mode via keyboard 42. The system responds bydisplaying on alphanumeric display 74 the physical distance between thecursors. Furthermore, in the preferred embodiment, each time ameasurement operation is performed, the system shown in FIG. 11 providespercent difference information with respect to the previous measurement.More specifically, the percentage by which the last measured distance issmaller than the previous measured distance is displayed on alphanumericdisplay 74. In angiographic applications, this may be used to determinean indication of the percentage of stenosis of a lumen by measuring thenormal width of the lumen followed by the contracted width.Specifically, the formula used for determining percentage is ##EQU1## Itis recognized that this information is available regardless of whether acalibration had been performed previously or not. In the preferredembodiment of the present invention, calibration and measurementprocessor 70 is implemented with software executed on the digital signalprocessor, but alternatively may be implemented with software executedon other special purpose or conventional general purpose processors, orby circuitry known to those of ordinary skill in the art.

Alphanumeric display 74 is conventional and is coupled to calibrationand measurement processor 70 and is adapted to display to the user thecalibration distance being adjusted and set by the user during thecalibration mode, as well as the measured distance and/or relativepercentage difference from a previous measurement during the measurementmode.

In operation of the preferred embodiment, the user, via keyboard 42,activates either cursor 1 positioning mode or cursor 2 positioning mode.This correspondingly enables either cursor 1 locator 62a or cursor 2locator 62b to be responsive to track ball 48. Then, the user adjuststhe location of the selected cursor via the track ball, and cursor imagegenerator 62c generates cursor image location data which it supplies tocursor overlay circuit 60. The cursor overlay circuit thereby combinesthe video signal from frame memory 16 with the cursor image locationdata produced by cursor generator 62. The result is then provided tovideo output circuit 20, which produces the final video output fordisplay on the video monitor.

The operation of the calibration and measurement functions are similar,except that in the calibration mode the user selects and locates cursor1 and cursor 2 at two respective points separated by a known distance.Track ball 48 is used to calibrate the cursor display, namely to set theknown distance, which provides calibration and measurement processor 70with the necessary scale information to enable it to compute thephysical distance between any two other points at which the cursors areplaced subsequently. Flow charts representing the manner in which thecalibration and measurement functions are performed are shown in detailin FIGS. 12A-12C.

In particular, FIG. 12A represents a calibrate procedure 76. First, instep 78, the user selects cursor 1 via keyboard 42, thereby activatingcursor 1 locator 62a and causing cursor image generator 62c and cursoroverlay circuit 60 to display one overlaid cursor on the video imagebeing viewed. Then, in step 80, the user adjusts track ball 48 to enablecursor 1 locator 62a to locate cursor 1 at a desired point which,preferably, is one of the two endpoints separated by a known distance.Next, in step 82, the user selects cursor 2 via keyboard 42, therebyactivating cursor 2 locator 62b and causing cursor image generator 62cand cursor overlay circuit 60 to display both overlaid cursors on thevideo image being viewed. Then, in step 84, the user adjusts track ball48 to enable cursor 2 locator 62b to locate cursor 2 at another desiredpoint which, preferably, is at the other endpoint of the known distance.The calibration mode is then selected in step 86 by pressing thecalibrate key on keyboard 42, and then track ball 48 is adjusted in step88 to set the known physical distance between the locations of the twocursors. In one embodiment an initial assumed distance (in millimeters)is displayed on alphanumeric display 74, and the subsequent adjustmentof the track ball causes the distance displayed to be changedaccordingly. When the distance displayed on the alphanumeric displayagrees with the known distance between the points located by thecursors, system calibration is "locked in" by pressing the calibrate keyon the keyboard 42 once again as shown in step 90.

FIG. 12B represents a measurement procedure 92 by which the user maymake a measurement to determine a physical distance. First, the usercalibrates the cursor display system by performing calibration procedure76. Next, in step 94, the user selects cursor 1 via keyboard 42, therebyactivating cursor 1 locator 62a and causing cursor image generator 62cand cursor overlay circuit 60 to display an overlaid cursor 1 on thevideo image being viewed. Then, in step 96, the user adjusts track ball48 to enable cursor 1 locator 62a to locate cursor 1 at a point which isone of the two endpoints of the distance to be measured. Next, in step98, the user selects cursor 2 via keyboard 42, thereby activating cursor2 locator 62b and causing cursor image generator 62c and cursor overlaycircuit 60 to display both overlaid cursors on the video image beingviewed. Then, in step 100, the user adjusts track ball 48 to enablecursor 2 locator 62b to locate cursor 2 at a point which is at the otherendpoint of the distance to be measured. Measurement mode is thenselected in step 102 by pressing the measure key on keyboard 42, and thesystem displays on alphanumeric display 74 the physical distance betweenthe two points marked by the two cursors.

FIG. 12C represents a measurement procedure 104 by which the user maymake a measurement to determine the percentage by which a measureddistance is smaller than the previous measured distance. It will be seenthat this procedure is substantially identical to measurement procedure92 for the measurement of a physical distance, except that the user neednot first calibrate the system. When the measurement mode is selected instep 102 by pressing the measure key on keyboard 42, the system displayson alphanumeric display 74 the percentage by which the measured distanceis smaller than the distance measured the last time a measurement wasmade, according to the formula shown above. If no previous measurementwas made, 100% is displayed.

Although the flowcharts of FIGS. 12A-12C represent the procedures to befollowed to perform calibration and measurement in accordance with thepreferred embodiment, the apparatus according to the present inventionmay be alternatively implemented in such a manner that other proceduresapparent to those of ordinary skill in the art are used to accomplishthese functions.

While particular embodiments of the present invention have beenspecifically illustrated and described, it is anticipated that variouschanges and modifications will be apparent to those skilled in the art,and that such changes may be made without departing from the scope ofthe invention as defined by the following claims.

What is claimed is:
 1. Apparatus for generating digital video signalsrepresenting a photographic image previously recorded in a frame on aphotographic film-type medium, comprising:image pickup means forproducing video signals in response to a light image of saidphotographic image projected thereto; digitizing means coupled to saidimage pickup means for digitizing the video signals produced thereby soas to provide corresponding digital video data; memory means for storinga video frame interval of said digital video data; enhancement meanscoupled to said memory means for selectively digitally enhancing saiddigital video data read from said memory means in accordance with aconversion function for providing enhanced video data; and a digitalsignal processor for controlling at least said image pickup means, saidmemory means and said enhancement means, and for supplying an operatorcontrolled conversion function to said enhancement means.
 2. Theapparatus of claim 1 further comprising signal output means coupled tosaid enhancement means for producing at least one output video signalfrom said enhanced video data.
 3. The apparatus of claim 2 wherein saidsignal output means includes means for producing said at least oneoutput video signal in digital format.
 4. The apparatus of claim 1wherein said image pickup means includes optical zoom means responsiveto drive signals for zooming in and out on said photographic image, andmanually operable control means for generating zoom selection signals;and wherein said digital signal processor is responsive to said zoomselection signals for supplying corresponding drive signals to saidoptical zoom means.
 5. The apparatus of claim 4 wherein said manuallyoperable control means for generating zoom selection signals includes atrack ball.
 6. The apparatus of claim 4, wherein said manually operablecontrol means includes means for selectively storing zoom datarepresenting an amount of zooming in or out on said photographic imageby said optical zoom means, and means for selectively generating zoomselection signals in accordance with said stored zoom data.
 7. Theapparatus of claim 1 wherein said image pickup means includes opticalpanning means responsive to drive signals for panning said photographicimage, and manually operable control means for generating pan selectionsignals; and wherein said digital signal processor is responsive to saidpan selection signals for supplying drive signals to said opticalpanning means.
 8. The apparatus of claim 7 wherein said manuallyoperable control means for generating pan selection signals includes atrack ball.
 9. The apparatus of claim 7 further comprising filmtransport means for transporting said film-type medium in apredetermined direction of motion to position a film frame for theprojection of said light image thereof; and wherein said optical panningmeans includes y--y panning means coupled to said film transport meansfor panning said photographic image by transporting said film-typemedium by said film transport means in said predetermined direction ofmotion of said film-type medium.
 10. The apparatus of claim 7 furthercomprising film transport means for transporting said film-type mediumin a predetermined direction of motion to position a film frame for theprojection of said light image thereof; and wherein said optical panningmeans includes x--x panning means for panning said photographic imagealong an axis of the film frame which is perpendicular to saidpredetermined direction of motion of the film-type medium.
 11. Theapparatus of claim 10 wherein said x--x panning means includes means forproviding relative movement between said film-type medium and said imagepickup means along the axis of the film frame perpendicular to thedirection of motion of the film-type medium.
 12. The apparatus of claim7, wherein said manually operable control means includes means forselectively storing pan data representing a position of panning by saidoptical panning means, and means for selectively generating panselection signals in accordance with said stored pan data position sothat said optical panning means pans said photographic image at saidrepresented position.
 13. The apparatus of claim 1, wherein saidenhancement means includes means for selectively stretching gray levelsof said digital video data.
 14. The apparatus of claim 1, wherein saidenhancement means includes means for producing enhanced video datarepresenting a negative image of said digital video data.
 15. Theapparatus of claim 1, wherein said digital signal processor is operableto supply different conversion functions to said enhancement means; andsaid enhancement means includes means for storing a newly suppliedconversion function, said enhancement means digitally enhancing saiddigital video data in accordance with a previously supplied conversionfunction when said newly supplied conversion function is not completelystored in said enhancement means.
 16. The apparatus of claim 1, whereinsaid enhancement means includes a look-up table for storing saidconversion function supplied by said digital signal processor, saidenhancement means digitally enhancing said digital video data read fromsaid memory means in accordance with said conversion function stored insaid look-up table.
 17. Apparatus for generating digital video signalsrepresenting a photographic motion picture previously recorded insuccessive frames on a photographic film-type medium, comprising:imagepickup means for producing video signals in response to light images ofeach of said successive frames of said photographic motion pictureprojected thereto; digitizing means coupled to said image pickup meansfor digitizing the video signals produced thereby so as to providecorresponding digital video data; memory means for successively storingat least one video frame interval of said digital video data;enhancement means coupled to said memory means for selectively digitallyenhancing said digital video data read from said memory means inaccordance with a conversion function for providing enhanced video datacomposed of successive frames representing said photographic motionpicture; and a digital signal processor for controlling at least saidimage pickup means, said memory means and said enhancement means, andfor supplying an operator controlled conversion function to saidenhancement means.
 18. The apparatus of claim 17 further comprisingsignal output means coupled to said enhancement means for producing anoutput video signal composed of said successive frames from saidenhanced video data.
 19. The apparatus of claim 18 wherein said signaloutput means includes means for producing said output video signal indigital format.
 20. The apparatus of claim 17 wherein said image pickupmeans includes optical zoom means responsive to drive signals forzooming in and out on each of said successive frames of saidphotographic motion picture, and manually operable control means forgenerating zoom selection signals; and wherein said digital signalprocessor is responsive to said zoom selection signals for supplyingcorresponding drive signals to said optical zoom means.
 21. Theapparatus of claim 20 wherein said manually operable control means forgenerating zoom selection signals includes a track ball.
 22. Theapparatus of claim 17 wherein said image pickup means includes opticalpanning means responsive to drive signals for panning each of saidsuccessive frames of said photographic motion picture, and manuallyoperable control means for generating pan selection signals; and whereinsaid digital signal processor is responsive to said pan selectionsignals for supplying drive signals to said optical panning means. 23.The apparatus of claim 22 wherein said manually operable control meansfor generating pan selection signals includes a track ball.
 24. Theapparatus of claim 22 further comprising film transport means fortransporting said film-type medium in a predetermined direction ofmotion to position each of said successive frames for the projection ofsaid light image thereof; and wherein said optical panning meansincludes y--y panning means coupled to said film transport means forpanning each of said successive frames of said photographic motionpicture by transporting said film-type medium by said film transportmeans in said predetermined direction of motion of said film-typemedium.
 25. The apparatus of claim 22 further comprising film transportmeans for transporting said film-type medium in a predetermineddirection of motion to position each of said successive frames for theprojection of said light images thereof; and wherein said opticalpanning means includes x--x panning means for panning each of saidsuccessive frames of said photographic motion picture along an axis ofthe frames which is perpendicular to said predetermined direction ofmotion of the film-type medium.
 26. The apparatus of claim 25 whereinsaid x--x panning means includes means for providing relative movementbetween said film-type medium and said image pickup means along the axisof the frames perpendicular to the direction of motion of the film-typemedium.
 27. The apparatus of claim 17 wherein said light images of saidsuccessive frames of said photographic motion picture are projected ontosaid image pickup means at a rate different from a rate at which saidsuccessive frames are provided in said enhanced video data.